Earthquake Rupture Forecast and Ground Motions Simulation for Maximum Expected Earthquakes along SE Spain: Simulations for 0-1 Hz using Cybershake

Southeast Spain experiences relatively low seismicity rates, characterized by slow seismic deformation. However, historical records highlight the significant impact of moderate to large earthquakes on local communities, such as the 1518 Vera (Almería) earthquake (Mw 6.4) and the 2011 Lorca earthquake (Mw 5.2). Thus, such events pose a considerable seismic risk to the region, in spite of their infrequent occurrence. Given the lack of comprehensive data on this kind of seismic events, this study contributes towards a physics-based seismic hazard model for Southeast (SE) Spain. Specifically, we first develop a broad earthquake rupture forecast (ERF) model that includes potential single- and multi-fault events, and then we use Cybershake to model the maximum-magnitude expected earthquakes along the various fault systems in the region, to obtain 0-1 Hz ground motion simulations. In this ERF model, we integrate a vast amount of regional geological data, including the Quaternary-Active Faults Database of Iberia, historical seismic catalogs, and available paleoseismic data as well. Using Cybershake, a high-performance computing earthquake-modeling platform originally designed for Southern California, we simulate ground-motion time histories from pseudo-dynamic kinematic rupture scenarios on three-dimensional finite faults. Our simulations consider a recently-available tomographic 3D velocity model, but for completeness, we also perform simulations using a 1D average model and explore the differences on the resulting synthetic ground motions. This approach allows to create physics-based rupture scenarios and shake maps, offering an alternative seismic hazard model tailored to SE Spain and setting the basis to update regional seismic hazard assessments. The results provide valuable insights into potentially harmful multi-fault events and scenarios in slow-deforming tectonic settings, contributing to more accurate seismic hazard and risk maps, and informing effective planning, decision-making and response strategies in the region.